JPS58164475A - Fluid-power assisting steering gear - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A fluid power assisted steering system generally consists of a fluid reservoir, a pressure generator, a distribution valve, and a double-acting power cylinder.

In many rotary type distribution valves, a plurality of rotary seals are provided between the valve body and the sleeve, and these seals isolate a number of passages inside the valve from each other. These passages are one for receiving pressurized fluid from the pressure generating device, one for communicating with the reservoir, and one for communicating with the cylinder chamber of the power cylinder.

A simple method of making these rotary seals is to machine a groove in the outer surface of the distributor valve sleeve into which a low coefficient of friction seal (e.g. made of PTFE) is fitted; forms the aforementioned passage between the sleeve and the valve body.

In open center distribution valves, when the valve is in its rest position, the fluid pressure between the various seals is substantially zero;
As a result, the seal is not subjected to any pressure and the friction between the valve body and the sleeve is extremely low. However, in the case of closed center distribution valves, the passageway connected to the fluid pressure generating device is permanently under pressure (e.g. 150
The two seals forming this passage are under constant pressure due to the presence of burs (of the burr), and even if the seals have a low coefficient of friction (the undesirable frictional torque between the valve body and the sleeve For example, for a pressure of 150 bar, a frictional torque of 0.2~o, amdaN) is generated.This frictional torque causes, for example, the spontaneous return of the running wheels to the neutral position (corresponding to the forward straight forward motion of the vehicle). This is a problem because it gives the impression that the steering accuracy of the vehicle is insufficient.

In order to eliminate this drawback, the present invention provides a power assist steering system equipped with a closed center type distribution valve, in which a pressure reduction device is interposed between the pressure generation device and the distribution valve, and the pressure reduction device is connected to the distribution valve. It is proposed that the pressure be controlled by the fluid pressure supplied from the valve to the cylinder chamber of the power cylinder.

With this arrangement, the seal of the distributor valve sleeve is only subjected to a reduced pressure when the distributor valve is in the rest position and the supply pressure to the cylinder chamber is very low. As a result, friction between the components of the distributor valve is significantly reduced and steering accuracy is improved.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, in the known device shown in FIG. 1, the power-assisted steering device basically consists of a low-pressure fluid reservoir lO, a pressure generating device 12 consisting of, for example, a pump 12a and an accumulator x2b, and a four-sided open center type. It consists of a distribution valve 14, which is a valve, and a power cylinder 16, which has two chambers 16a and 16b.

These components are connected by the following lines. namely, one line 18 between the pressure generator 12 and the distribution valve 14, one line 20 between the distribution valve 14 and the reservoir 10, and one line 20 between the distribution valve 14 and the two Q cylinders u 16a and 16.
There are two lines 22 and 4 between b and da.

The distribution valve 14 is, for example, according to French Patent No. 2.382.36.
The type disclosed in No. 1 can be adopted. This distribution valve has a rotary sleeve fitted into the valve body, and a plurality of rotary seals arranged between the sleeve and the valve body to form four passages connected to the above-mentioned lines. The structure is as follows.

The distribution valve is of a so-called closed center type, and is constructed as follows in its rest position.

One line 18 and the passageway connected to the pressure generator are blocked. Therefore, the pressure is the same as the output pressure of the pressure generator.

- the line 20 and the passageway connected to the reservoir are at the same pressure as the reservoir; (Typically atmospheric pressure) One line 22 and 24 and two passages connected to the cylinder are the pressures present in the reservoir.

As a result, the rotary seal separating the first passage from the rest of the distribution valve is subject to the full supply pressure of the pressure generating device, and for this reason there is a gap between the seal and the sleeve on the one hand and on the other hand. High frictional forces develop between the seal and the valve body, resulting in the disadvantages discussed above.

Next, FIG. 2 showing a power assisted steering system according to the present invention will be explained. This apparatus includes several components that are substantially the same as those of the apparatus shown in FIG. 1, and the same reference numerals have been used.

In particular, the pressure generator 12, the distribution valve 14, the cylinder 16 and the lines 18.20, 22.24 are also present in this device.

A pressure reducing device 26 is interposed in the line 18 between the pressure generating device 12 and the distribution valve 14, so that the line 18 is divided into two parts. That is, the first line 18a is I
The second line 18b is connected to the FJ generator 12, and the second line 18b is connected to the distribution valve 14.

The pressure reducer is connected to lines 22 and 24 by tubes 28 and 30 and to reservoir 10 by tube 32.

The detailed structure of the pressure reducing device 26 is shown in FIG.

The device includes a continuous hole section 36a of progressively increasing diameter.
, 36b and 36C.
has.

A pressure reducing reciprocating member 38 having two bearings 40 and 42 having the same diameter as the diameter of the hole portion 36a and separated by a small diameter portion 44 is slidably fitted into the smallest diameter hole portion 36a. It has been done. This small diameter portion 44 forms an annular chamber 45 within the bore.

Three ports communicate with this part of the hole.

That is, an inlet port 46 connected to line portion 18a.
, an outlet boat 48 connected to line section 18b, and a discharge port 50 connected to tube 32.

The outlet port 48 is located midway between the other two boats with respect to the axial direction, and the separation between the proximal edges of the inlet port 46 and the outlet port 50 is approximately equal to the smaller diameter portion of the reciprocating member. The length is slightly larger than 44. A plug 52 closes the end of the hole 36a and cooperates with the reciprocating member 38 to form a balance chamber 54 that communicates with the annular chamber 45 on the outer periphery of the small diameter portion 44 through a passage 56 inside the reciprocating member. .

A control device 58 is housed at the end of the main body 34 on the opposite side from the reciprocating member side. The control device includes a bushing 6o secured within the largest diameter portion 36c of the bore 36 and retained by a plug 62. A central hole 64 of the bushing 6o has the same diameter as the hole portion 36a and slidably houses a control bottle 66.

Two control rooms are thus formed. first chamber 6
8 is formed between the control pin 66 and the plug 62 and is connected via a port 70 provided in the plug 62 to the tube 28, ie to the chamber 16a of the cylinder. Also second chamber 7
2 is formed between the pin 66 and the reciprocating member 38, and the hole 3
Hole 7 provided in the body at intermediate diameter portion 368 of 6
4 to the tube 30, ie to the chamber 16b of the cylinder.

Control pin 66 includes an axial extension 76 extending toward reciprocating member 38 . A spring 78 is housed in the second control chamber 72 surrounding the extension 76, and one end of the spring 78 is supported by the reciprocating member 38 via a pad 8o.
The other end is supported on the bush 60 via a collar 82 surrounding the extension 76 of the bottle 66.

The pressure reduction device operates as follows. The discharge pressure of the pressure generator is introduced into the inlet port 46 and the annular chamber 45, and is further supplied to the equilibrium chamber 54 through the passage 56. ing.

When pressure is introduced, the pressure reducing reciprocating member 38 compresses the spring 78 and moves toward the control chamber 72 . During this movement, the annular chamber 45 changes its position and, as a result of the cooperation of the inlet port 46 and the outlet port 50, a reduced pressure is created in this chamber, and the reciprocating member 38 is forced to move the said reduced pressure into the spring 78. It takes a healing position that is a function of the residual spring force.

As a result, a reduced pressure is introduced into the inlet passage of the distributor valve 14 and the friction caused by the rotary seal is reduced to a small value.

When the reciprocating portion '#38 is in its equilibrium position, the pad 8
Note that a gap 1aI is formed between 0 (shown in dotted lines) and the extension 76. This gap is smaller than the gap Wb1 between the shoulder portion 84 of the pin 66 and the collar 82.

When the distribution valve 14 is actuated, for example in the case of a left turn,
A passage connected to the cylinder chamber 16a is cut off from the reservoir and communicated with the inlet passage.

Therefore, the pressure within the cylinder 16a increases, and the pressure within the first control chamber 68 of the pressure reducing device 26 also increases. The control pin 66 moves closer to the depressurizing reciprocating member 38 without compressing the spring 78 and finally releases the pad 80.
comes into contact with.

The control pin 66 thus exerts an additional force on the reciprocating member 38, causing the reciprocating member 38 to move toward the balance chamber 54 and the inlet port 46 opening again into the annular chamber 45. Therefore, the pressure transmitted from outlet port 48 to distribution valve 14 increases;
As a result, the pressure transmitted from the distribution valve 14 to the cylinder chamber 16a also increases, providing full power assistance to the steering system.

The reciprocating member 38 is connected to the cylinder chamber 16a by the distribution valve 14.
will assume a new equilibrium position that is a function of the pressure transmitted to the

When the distributor valve 14 returns to its rest position, the two cylinder chambers 16a, 16b and the two control chambers 68, 72 are connected to the reservoir, and the control pin 66 returns to its initial equilibrium position, in which the distributor valve 14 The pressure transmitted to is significantly reduced.

Also when the distributor valve 14 is actuated in the opposite direction, i.e. in the case of a right turn, for example, the increase in pressure in the second control chamber 72 exerts a fluid force directly on the reciprocating member 38, causing the control pin 66 to The pressure reducer 26 operates in the same manner, except that it remains in its retracted position.

To reduce friction between the reciprocating member 38 and control pin 66 and the body 34, these components do not include seals. These are preferably provided with a suitable number of expansion grooves 86,88 which prevent the reciprocating member 38 and control pin 66 from becoming stuck in their respective holes.

In this way, the response time of the pressure reducing device is kept as low as possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a known power-assisted steering device, FIG. 2 is a schematic diagram of an embodiment of the power-assisted steering device of the present invention, and FIG. 3 is a sectional view of the pressure reducing device in FIG. 2. . 10...Fluid reservoir, 12...Pressure generator, 14...
- Distribution valve, 16... Power cylinder, 26... Pressure reducing device.

Claims (1)

[Claims] 1. A fluid reservoir (10), a pressure generating device (12), a closed center distribution valve (14), and a double-acting power cylinder (16), the above-mentioned A pressure reducing device (26) is provided between the pressure generating device (12) and the distribution valve (14), and the pressure reducing device is operated by the distribution valve to reduce the pressure in the cylinder chambers (16a, 16b) of the power cylinder.
) A fluid power assisted steering device characterized in that it is controlled by fluid pressure supplied to the steering device. 2. The pressure reducing device (26) is connected to the hole portion (3) of the hole (36).
6a), a reciprocating member for reducing pressure (
a main body (34) slidably housing a main body (38); an inlet port (46) connected to the pressure generating device (12); and an outlet port) (48) connected to the distribution valve (14).
) and a discharge port connected to the reservoir (10)).
(50), all of the three ports communicate with the hole portion (a6a), and the exit boat (48
) is arranged between the other two ports in the axial direction, and further includes the inlet port (46) and the outlet port (50).
and are arranged at an axial distance greater than the length of the small diameter portion (44), and the reciprocating member (38)
is formed in said hole portion (36a) an equilibrium chamber (54) which communicates with said small diameter portion (44) via a passageway (56), and furthermore, said hole (36) O-another portion (36b). ,
36C) includes a spring (78) that presses the reciprocating member (38) for depressurization toward the equilibrium chamber (54), and a spring (78) that is coaxial and the same diameter as the reciprocating member (38) for depressurization and is located within the main body. A control pin (66) separating the first control chamber (68) and the second control chamber (72) is stored, and the second control chamber (72) houses the reciprocating member (38) and the control pin (66). 66)
The fluid according to claim 1, characterized in that the control chamber (68° view 72) is connected to the cylinders (16a, 16b) of the power cylinder, respectively. Power-assisted steering system. 3. The control pin (66) is connected to the pressure reducing reciprocating member (3).
8) an extension (76) extending in the direction 4, the spring (78) being supported by the main body (34) via a collar (82) surrounding the extension (76); A fluid power assist steering device according to claim 3, characterized in that: 5. Any one of claims 2 to 4, wherein the reciprocating member (38) and the control pin (66) each have an expansion groove (86, 88) on their outer periphery.
The adult power assisted steering device described in paragraph 1.